# Definition for a binary tree node.
import collections
class TreeNode(object):
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

class Solution(object):
    def trimBST(self, root, L, R):
        """
        :type root: TreeNode
        :type L: int
        :type R: int
        :rtype: TreeNode
        """
        if not root :
            return None
        if root.val < L:
            return self.trimBST(root.right,L,R)
        elif root.val >R:
            return self.trimBST(root.left,L,R)

        root.left = self.trimBST(root.left,L,R)
        root.right = self.trimBST(root.right,L,R)

        return root


m1 = TreeNode(3)
m1.left = TreeNode(0)
m1.right = TreeNode(4)
m1.left.right = TreeNode(2)
m1.left.right.left = TreeNode(1)

s = Solution()

t = s.trimBST(m1,1,3)
print(t)
